He later told police: "I'm sorry. I didn't mean it. If I could not have her then nobody can."

Tom Crowther, defending, said his client's life had "centred on his relationship with Ms Williams" and her texts had "extinguished any hope" of a reconciliation.

Mr Crowther said: "He is very, very sorry for what he did on that night."

The judge, Justice Wyn Williams told him: "Having discovered that Rebecca Williams had taken up with another man you stabbed her in a fit of jealous rage.

"One stab had penetrated her liver and the probability is that but for medical intervention she would have died."

After the sentencing, Det Insp Iwan Jones, of Dyfed-Powys Police, called the crime "premeditated and vicious".

He said: "It's a substantial term of imprisonment and is appropriate for this crime.

"It also sends a strong message that domestic violence will be dealt with severely by the courts and will hopefully offer encouragement to others suffering from domestic violence that they can come forward to us and report it."